Steam turbine designs include static nozzle assemblies that direct the flow of a working fluid such as steam into rotating buckets that are connected to a rotor. In steam turbines, the nozzle (airfoil) construction is typically called a “diaphragm” or “nozzle assembly” stage. Turbine diaphragms are assembled in two halves around the rotor, creating a horizontal joint between these two halves. Diaphragm centering pins are used to position the diaphragms in the transverse direction during installation. These centering pins are also designed to take the torque load generated by the diaphragm.
The centering pin is traditionally installed in an area of the diaphragm assembly with a small interference. The centering pin is traditionally cooled (e.g., frozen) to a point in which it contracts to fit in this area of small clearance. This often requires the use of dry ice or another severe cooling mechanism during installation, e.g., in the field. However, the unavailability and relatively high cost of these severe cooling mechanisms can be undesirable. Additionally, freezing and thawing of the centering pin can cause mis-alignment of the turbine diaphragm.